The invention relates to a bolt for a conveyor belt fastener used in belt splices and, more particularly, to a conveyor belt fastener bolt that allows splices to be applied more easily and quickly and with improved strength.
Most belt fasteners used for making belt splices have an upper member or plate and a lower member or plate that are clamped on opposite surfaces at a belt end portion that is to be spliced to another belt portion. Solid plate fasteners utilize a single plate on the upper surface and a single plate on the bottom surface spanning both end portions of the conveyor belt, whereas hinge fasteners have arcuate hinge loops that connect the upper and lower plates and which mate with loops of fasteners attached to the other belt end portion for receiving a hinge pin therethrough to provide a hinged splice. The present invention is directed to a bolt that is used with belt fasteners of either type of the above-described fasteners, i.e. solid plate or hinge fasteners.
Present conveyor belts can have a wide variety of constructions designed according to the rigors of the applications which they must withstand. The mechanical fastener chosen for a conveyor system requires taking into account the tensile strength of the belts employed and the pulley diameters in the conveyor drive system from which the belts are to be run. Conveyor belt materials are typically of a rubber or PVC construction and with various strengthening compounds, include woven materials and/or have plies of different materials running therethrough to improve the belt tensile strength. The covers of conveyor belts particularly in heavy-duty applications will have a tough, rugged construction to provide the necessary durability for the abrasive and heavy materials usually transported thereby.
With the mechanical solid plate or hinged fasteners that use bolts for clamping the plates onto the opposite surfaces of the belt end portions, one of the major considerations is the installation time and the ability of the applied fasteners to provide a good, strong splice. In both the bolt hinged and solid plate fastener systems, a template is used for forming through holes in the belt end portions for receiving the bolts of the fasteners therethrough. The punch or bores are driven as by a power tool through openings in the template into the belt carcass for accurately forming the through holes for proper fastener alignment. Inserting the threaded shanks of the bolts into and through the holes in the belt end portions can be a very difficult and time consuming task. Where the holes in the belt are tightly formed so that there is little loose play between the shank and the belt carcass material about the hole, the shank threads tend to get hung up on the belt carcass as the worker attempts to push the bolts through the holes in the belt. Because these belts are typically of very tough and rugged construction as previously described, this pushing of the bolts through the holes can take a significant amount of time and effort. With the bolt solid plate fasteners, after all bolts are inserted through the first belt end portion there remains the task of placing the holes of the other belt end portion onto the bolts of the fasteners already in place on the first belt end portion. For this purpose, the template has a comb-like edge with notches for receiving the bolts to be inserted in the belt end to help keep them aligned during this process; however, the bolts are still not totally confined and do tend to move around particularly as the worker encounters difficulty as they push the belt down onto the bolts for being inserted through the holes.
After repeated usage, the edges about the guide holes in the templates can become deformed because of engagement with the driven punch distorting the holes from their desired circular shape. Deformed template holes usually lead to inconsistent, ragged through holes formed in the belt end such as with an oval cross-sectional shape. While this provides for easier installation of the bolts through the larger ovalized through holes, there is also a greater amount of belt carcass material removed and more play between the hole walls in the belt end and the shank of the bolt therein. The larger holes and looseness of the fit between the bolts and holes in the belt end produces a weaker splice over one where the shanks of the belts are snugly received in tightly formed holes with a circular cross-sectional shape.
With the distal ends of the bolts projecting through the holes, nuts are next placed on the projecting ends of the shanks and held thereon by starting the threading of the internal threads on the nut with the threads on the shank. This presents a significant limitation in the use of current bolt fasteners, since it is often very difficult for a worker to start the threading by hand as they are often performing splicing operations in extreme conditions such as where there is poor lighting and/or in extreme cold temperatures. In the latter case, the worker is often wearing gloves making it very difficult to have the necessary tactile coordination to start the thread properly. With current bolts, there is only a very small conical lead-in tip portion at the end of the bolt onto which the nut is placed. In this position, the nut can shift around so that it is at an angle to the axis of the bolt shank, and starting the threading in this angled orientation tends to produce cross-threading between the nut and shank. A nut that is cross-threaded makes it very difficult for the wrenching operation to properly seat the nut in the aperture of the upper plate as is desired for providing the fastener with its maximum holding power and the resultant strong splice. In addition, backing the nut off the shank to avoid screwing down the nut in its cross-threaded orientation on the bolt shank is also difficult and increases installation time.
Even where the nuts have been threaded properly to the shank, when a power wrench is employed to screw the nuts down for clamping the fastener plates against the belt end portion, vibrations associated with use of the power tool can cause the nuts to loosen and fall off the ends of the shanks requiring the nuts to be picked up and placed back thereon or having the worker retrieve additional nuts for placing on the shank end. Oftentimes, splicing is occurring at an elevated location and if the nuts fall to the ground below, the worker may not have a sufficient number of nuts at the elevated location for completing the splice without having to travel down to the ground level for obtaining additional nuts generating additional delays during the installation process.
It has also been found that during shipping and handling the endmost threads on the bolt shank can be damaged adding to the difficulty in threading nuts thereto. In addition, during the installation procedure, the plates may be pounded as with an impact tool to sink teeth thereof into the belt carcass. If the impact tool inadvertently contacts the projecting shank end, the threads most likely to be damaged are those at the end thereof creating the adverse consequences for starting the threading of the nut described above.
In accordance with the present invention, a fastener is provided for splicing end portions of conveyor belts together with the fastener having a bolt with a pilot or lead-in portion that provides improved threading of a nut thereto and makes installation of the fasteners on the belt ends faster and easier. The pilot of the bolt is longer than the beveled conical tip portion of prior belts so that nuts received thereon will stay substantially aligned with the axis of the shank. In this manner, threading of the nut to the bolt shank is easier in terms of avoiding cross-threading problems. Also, as the pilot portion of the shank is free of any threads, the installation of the bolt onto the belt ends can be done more quickly with less resistance during the insertion process. With the threading of the nuts started on the bolt shank threads, the nuts are less likely to fall off the piloted shank when a power wrench is used to screw the nuts down for clamping the plates of the fastener about the belt end as even if the nuts become unthreaded from the shank, the pilot portion will hold the nuts thereon.
In one form of the invention, the fastener includes a pair of plates each having at least one aperture extending therethrough, and a bolt including an elongate shank having opposite ends thereof. A plurality of threads are formed along the shank. A nut is provided having internal threads for being threaded to the shank threads with the shank projecting through a hole in one of the conveyor belt ends and through the aperture of each of the plates. A pilot portion of the shank is at one of the ends thereof and has a surface free of threads extending about the shank. The surface has a predetermined length along the shank to allow the nut to be readily fit onto the shank via the pilot portion thereof. With the nut on the pilot portion, threads of the nut are in a predetermined orientation to address the shank threads for properly threading the nut to the shank reducing instances of cross-threading thereof. This is in contrast to the beveled end tips of prior bolts which allow nuts to be shifted about when a worker starts to thread the bolt to the shank increasing the likelihood of cross-threading and the attendant problems therewith.
In one form, the shank has a longitudinal axis and the nut has an internal axis substantial aligned with the shank axis with the nut received on the pilot portion of the shank. Accordingly, the pilot portion maintains the nut axis substantial aligned with the nut axis so that the threads engage each other in the proper orientation to avoid cross-threading.
In another form, the shank pilot portion has a section that is cylindrical in shape with a predetermined diameter and the threads of the nut have a predetermined diameter. The diameter of the nut threads is greater than the diameter of the pilot surface by a predetermined amount so that the nut threads readily clear the pilot cylindrical surface when fit thereon. In this manner, the pilot portion guides the nut along the surface thereof before a worker is required to start the threading process between the nut and the shank. This makes installation easier especially given that the pilot also aligns the nut in the afore-described orientation where it addresses the shank threads to facilitate proper threading of the nut to the shank after it has been slid down the pilot portion to the shank threads.
In a preferred form, the nut has a body having an inner annular surface including the internal nut threads thereon and aligned about an internal axis of the nut, and the nut body has a predetermined thickness along the nut axis that is approximately equal to or less than the predetermined length of a pilot portion to keep the nut thereon during fastener application operations. Because the pilot portion is as long or longer than the nut, even if the nut works its way unthreaded from the shank, it is unlikely to fall off the pilot portion as it will still project to the level of or beyond the top of the nut in contrast to prior bolts where if the nut was to work its way unthreaded during fastener application operations, it would in all likelihood fall off the small conical tip at the end of the shank necessitating replacement of the nut slowing down the installation process.
In another form of the invention, a fastener is provided for splicing end portions of conveyor belts having tough, rugged carcasses in which holes are preformed through the end portions for receiving bolts therethrough. The fastener includes an elongate bolt shank having proximate and distal ends thereof and an axis along which the shank extends. An enlarged head portion is at the proximate end of the shank for being seated in the aperture of one of the plates. A plurality of threads are formed on the shank adjacent the head portion and extending toward the distal end of the shank. A non-threaded lead-in portion is provided at the distal end of the shank. The lead-in portion has a predetermined length from the distal end that is sized to guide the shank during insertion thereof through one of the preformed holes in the belt end portion minimizing the force required to push the shank through the hole. The long lead-in portion, starts the bolt as it is inserted through the through holes for the predetermined length of the lead-in portion before it hits any threads on the shank so the worker pushing the bolt through the belt end hole can more easily complete this process without experiencing hang-ups of the shank threads on the tough carcass material surrounding the hole.
In one form, the lead-in portion has a section that is cylindrical in shape with a predetermined diameter that is smaller than the diameter of the threads on the shank to lead and guide the shank for rapid insertion through the preformed hole for faster fastener application operations.
In another aspect of the invention, a method of splicing end portions of conveyor belts having tough, rugged carcasses is provided. The method includes fixing a template having holes therein to at least one of the end portions to be spliced, driving a sharp hole forming tool through a template hole and through the belt carcass, forming a tight hole through the belt end portion aligned with the template hole to minimize the amount of belt carcass material removed in forming the hole, providing a fastener having plates with apertures and at least one bolt having a shank with threads thereon, manually inserting a non-threaded lead-in portion of a bolt shank into the hole at one end thereof, advancing the shank through the tight hole with a minimum of hang-ups of the threads on the belt carcass about the hole, fitting an internally threaded nut on the lead-in portion projecting out from the other end of the hole, and threading the nut to the threads on the shank to clamp the fastener plates on opposite surfaces of the conveyor belt at the one end portion thereof to provide a high strength belt splice.